I. Field of the Invention
The present invention relates to a newly constructed transport plug which can pneumatically transport solid materials efficiently at a low speed in a transport pipe having curved portions such as a bend pipe and to a pneumatic transport method in which solid materials are pneumatically transported at a low speed by the use of the transport plug.
II. Prior Art
The applicants of the present invention have proposed a pneumatic transport method and a pneumatic transport system wherein solid materials such as medical tablets are pneumatically transported at a low speed without causing cracks and breaks by the use of a transport plug comprising two bodies and flexible connecting means in Japanese Patent Application JP-A-H2-196002. (filed on Jul. 24, 1990)
According to the proposed method, as shown in FIG. 4, a transport plug 102 comprising two bodies 102a, 102b and flexible connecting means 102c is located at a starting position under a material insert port 101 provided at an initial end of a transport pipe 100 having bend pipes 100a and 100b. A fixed amount of weighed solid materials is fed into a storing space between the two bodies 102a, 102b of the transport plug 102, and the transport plug 102 filled with the solid materials 103 is pneumatically transported by the use of a pressurized transport gas supplied from the initial end of the transport pipe 100 toward the rear body 102b of the transport plug 102. Then the transport plug 102 is transported into a collector 106 connected at a terminal end of the transport pipe 100 and provided with a zigzag shooter 106a at its bottom. Thereafter, the transport plug 102 finishes transporting the solid materials, gas supply means (not shown) stops supplying gas and switches to suck air in the transport pipe 100, and the transport plug 102 is sucked and returned to the start position directly under the material insert port 101. Then next fixed amount of solid materials is fed into the storing space between the two bodies 102a, 102b of the transport plug 102 and the transport plug 102 is pneumatically transported by the use of the pressurized gas supplied into the transport pipe 102. Such steps are repeatedly performed and solid materials are successively transported into the collector 106 without causing any cracks or breaks.
In order to obtain a large transport capacity at one time and to facilitate feeding of solid materials, it would be preferred to make an inside diameter of the material insert port 101 provided at an initial end of the transport pipe 100 as large as possible adapting to an inside diameter of the transport pipe 100.
And when the inside diameter of the material insert port 101 is formed almost the same as that of the transport pipe 100, of which sectional view is shown in FIG. 5(c), relatively large amount of solid materials 103 would be filled in the storing space between the two bodies 102a, 102b of the transport plug 102, as shown in FIG. 5(a). However, when the transport plug 102 transfers into the transport pipe 100 from the material insert port 101, the top of heaped solid materials would be cut by rubbing with an upper wall of the transport pipe 100 and some of the cut materials would fall over the rear body 102b. And further, when the rear body 102b reaches under an opening of the insert port 101, the rear body 102b would be lifted. As the result, a gap would be made between the rear body 102b and a lower inside wall of the transport pipe 100, and some of the solid materials 103 would leak from the space, as shown in FIG. 5(b).
Generally, a tapered material insert port 101' having a smaller inner diameter than the transport pipe 100, as shown in FIG. 6(c), is provided at an initial end of the transport pipe 100 in order not to lift the rear body 102b of the transport plug 102 when the rear body 102b reaches under the opening of the insert port 101'. However, when solid materials 103 are fed into a storing space between the bodies 102a, 102b of the transport plug 102, the fed materials 103 would heap highly in the insert port 101' because of an angle of repose of the solid materials and a filling rate of the materials would become low, as shown in FIG. 6(a).
And further, when the transport plug 102 filled with solid materials 103 is transferred into the transport pipe 100 by the use of a transport gas, some of the solid materials 103 would be cut by rubbing with an upper wall of the transport pipe 100 and some of them would fall over the rear body 102b and some of them would be caught between the rear body 102b and the upper wall of the transport pipe 100, as shown in FIG. 6(b).
In addition, when the transport plug 102 containing solid materials 103 is transported upwardly in a curved portion 108, such as a bend pipe, of the transport pipe 100, the connecting means 102c would bend corresponding to a bending rate of the bend pipe. Consequently, as shown in FIG. 7 a crescent-shaped space g' is created between the bodies 102a, 102b and an upper inner wall of the curved portion 108. In this situation, when the space g' becomes larger than the particle size of the solid materials 103 or the same as the particle size, some of the materials 103 would drop out of the transport plug 102 or they would be caught in the space g' when the materials 103 are transported.
If some solid materials are dropped or caught in the transport pipe 100 while they are fed or transported, such materials would become obstacles and be cracked or broken when the transport plug 102 is returned to the starting position. It should be noted that this is considered to be an important and unignorable problem in order to transport solid materials by the use of the transport plug 102 in the transport pipe 100 without causing any cracks or breaks.